1. Field of the Invention
The present invention relates to a photosensitive resin derived from saponified poly(vinyl acetate), a photosensitive resin composition containing the resin, and a pattern formation method making use of the composition, and more particularly, to such a resin and resin composition which can be developed with an aqueous developer and which, when hardened, exhibits excellent water resistance and patterning characteristics, and to a pattern formation method making use of the composition.
2. Background Art
Conventional water-soluble photosensitive resins which are derived from saponified poly(vinyl acetate) (hereinafter referred to as "saponified PVA photosensitive resins") include those having a pendant group derived from a styryl derivative having a quaternary aromatic nitrogen-containing heterocyclic ring and are disclosed in, for example, Japanese Patent Publication (kokoku) Nos. 56-5761, 56-5762, and 2-276806 and Japanese Patent Application Laid-Open (kokai) Nos. 56-11906, 59-17550, 2-118575, and 6-43645. Although these photosensitive resins have high photosensitivity, hardened products thereof have poor water resistance and swell during development and thereby provide insufficient resolution in pattern formation.
Japanese Patent Application Laid-Open (kokai) No. 2-160807 discloses a saponified poly(vinyl acetate), as a saponified PVA photosensitive resin, containing a pendant group derived from a styryl derivative having a quaternary aromatic nitrogen-containing heterocyclic ring which pendant group has a betaine structure. However, this photosensitive resin has drawbacks, such as relatively poor photosensitivity and poor developability attributed to low water-solubility. As described above, conventional saponified PVA photosensitive resins have drawbacks such as poor water resistance when they become hardened, poor heat resistance, insufficient water solubility, and poor developability.